The Vermont Agency of Natural Resources
Air Quality
Air quality affects nearly every aspect
of life in Vermont. The fate of our acid
sensitive takes and streams, the growth
and productivity of our forests and
agricultural crops, the visual clarity
of our scenic mountain vistas, the accumulation
of toxic metals in fish and wildlife, and
Vermonters' health and welfare are all
influenced, by the levels of pollution
present in our air.
Vermont is one of the most rural states
in the nation, and its air quality is
generally superior to more densely populated,
industrialized regions. While Vermonters
rarely see thick, noxious plumes belching
from industrial smokestacks, the state's
air quality is far from pristine. Local
emissions from small sources like woodstoves,
increasing automobile and truck traffic, and
pollutants migrating into the state from
upwind regions frequently combine to produce
visible air pollution in Vermont, as well
as less visible but potentially more
significant environmental problems.
RESPONSE AND PROGRESS
Twenty-five years ago, air pollution control efforts
in Vermont and the nation were just getting underway.
The passage of the I 970 federal Clean Air Act, and
the formation that same year of the U.S.
Environmental Protection Agency and the Vermont
Air Pollution Control Program represented the
first significant attempts to measure the quality
of our air and to control air pollution sources.
The earliest efforts in Vermont and the nation
focused upon the largest, most obvious sources
of pollution. Open burning dumps spewed tons of
carbon monoxide, particulate matter, and toxic
metals into Vermont's air.
Industrial combustion sources burned coal or
high sulfur oil with no controls on fly ash or
sulfur dioxide emissions. automobiles burned
leaded gasoline causing high concentrations of
lead in the air, and contributed to elevated
lead blood levels in children.
Over time, emissions from these large obvious
sources have been substantially reduced or
eliminated. Stringent controls on stationary
sources and the elimination of lead from gasoline
have produced dramatic reductions in airborne
lead levels. Vermont's air lead levels have
declined by more than 99% from the mid 1970s,
and are currently well below federal air
standards (Fig. 1). Improvements in combustion
efficiency at stationary sources and reductions
in federal automotive emission standards have
cut carbon monoxide (CO) levels in Vermont by
more than 50% since the mid-70s (Fig. 1).
Vermont sulphur dioxide (SO2) levels have
declined by about 4o% since the 1970S due
to effective emission controls and the use
of low sulfur fuels at stationary sources
(Fig. 1). While Vermont atmospheric air
levels of SO2 are well below federal standards,
sulfur emissions transported from upwind states
continue to threaten Vermont's environment and
quality of life. Acid rain has acidified some of
our sensitive high elevation lakes and streams,
and sulfate (SOx) haze frequently obscures our
scenic Green Mountain vistas. National SOx
emissions have been reduced by 27% between
1970 and 1992, and further declines are expected
due to acid rain control provisions in the 1990
Clean Air Amendments.
PROBLEMS REMAIN
Despite growth in population, automotive traffic,
energy consumption and industrial productivity,
the trends in concentrations of most air pollutants
in Vermont have been downward. Overall, Vermont
emissions are currently the lowest in the nation.
On a per capita basis, however, the state ranks
only about average, emitting slightly more than
1200 pounds of volatile organic compounds (VOCs),
nitrogen oxides (NOx), and carbon monoxide (CO)
per person in 1992 . . . a rate higher than many
of our neighboring states.
As large stationary sources are controlled, our
emissions are less heavily influenced by large
industries, and increasingly dominated by individual
human activities such as heating our homes and
driving our cars. Automotive traffic in Vermont
has more than doubled since 1970, and the per
capita mileage traveled on Vermont highways is
higher than all but six other states. Today,
motor vehicles account for roughly 60% of statewide
emissions of VOCs and CO and nearly 80% of NOx emissions.
While levels of many air pollutants in Vermont have
declined significantly in recent years, concentrations
of ground level ozone have remained virtually
unchanged since the 1970S. Formed from reactions
of NOx and VOCs in the presence of
sunlight, ground level ozone poses a threat to
human health and the environment, including
damage to sensitive trees like white ash and
black cherry. Vermont’s ozone levels come
close to exceeding federal standards each
summer, and frequently exceed levels considered
unhealthy in other developed countries (Fig- 2).
Over the past 25 years, improved automotive
emission standards have produced substantial
reductions in the VOC and NOx emissions from
the average car on Vermont's highways.
Unfortunately, these gains have been offset
by increased vehicle use (Fig- 3).
As a result,
total motor vehicle emissions of VOCs have
declined only slightly over the past two decades
and, in the case of NOx, total emissions have
actually increased (Fig. 4) - If current growth
rates of vehicle traffic continue into the future,
statewide emissions of both NOx and VOCs will
start to increase over the next few years despite
further reductions in automotive emission standards
for new cars (Fig. 4). Growth in motor vehicle
emissions can be offset in the short term by the
implementation of a motor vehicle inspection and
maintenance program.
The average car emits about half a ton of air
pollutants each year. A car that is poorly
maintained or malfunctioning (so-called "super
emitters") may emit more than ten times this
amount. While these cars make up less than 10%
of all automobiles, they account for nearly 50%
of total automotive VOC emissions. I/M would reduce
VOC and CO emissions by about 33% and NOx
emissions by about 15%. By insuring that control
devices required on cars are working properly, an
I/M program would also result in fuel savings that
often offset the cost of the repair.
While projected increases in NOx and
hydrocarbon emissions raise serious concerns
about current and future ozone concentrations
in Vermont, increasing automotive emissions of
toxic air pollutants may pose an even greater
threat to Vermonters. Automotive and auto-related
emissions (i.e. gasoline evaporation and refueling)
dominate our statewide emissions of certain cancer-causing
pollutants like benzene and I-3 butadiene.
In Chittenden County alone, motor vehicles are
estimated to account for nearly 200,000 pounds of
benzene and 35,000 pounds Of 1-3 butadiene each year.
Although the state has only recently initiated ambient
air measurement of these toxic contaminants, the first
six months of data suggest that Vermont's annual Hazard
Ambient Air Standards for benzene and i-3 butadiene are
exceeded by a factor of 2 in small towns like Waterbury,
and by nearly a factor of 10 in more densely populated urban centers like Burlington.
CHALLENGES
In the near term, federal, regional, and state regulatory programs can make an important contribution to improving the quality of Vermont’s air. In the longterm, however, we may need to reconsider and change our increasing dependence upon the single passenger, gasoline-powered motor vehicle. Ultimately, our future air quality will depend upon critical choices made by individual Vermonters.
Some steps we can take to improve Vermont’s air quality include:
- Support the adoption and implementation of an inspection and maintenance program.
- Install (Stage II) vapor recovery systems at gas stations.
- Continue to reduce automobile emissions through greater use of vehicles using alternative fuels
(e.g. propane and natural gas). California-type low-emission vehicles and electric vehicles.
- Decrease total vehicle miles traveled through ride-sharing and improved mass transit systems.
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